Encode and audio record-reproduce equipment



ENCODE AND AUDIO RECORD-REPRODUCE EQUIPMENT Nov. 28, 1967 B. N. WHITLOCK 4 Shets-Sheet 1 Filed Jan. 21,

AGENT Nov. 28, 1967 B. N. WHITLOCK ENCODE AND AUDIO RECORD-REPRODUCE EQUIPMENT Filed Jan. 21, 1965 4 Sheets-Sheet 5 FIG. 7

INVENTOR BRUCE N. WH/TLOCK N 1967 B. N. WHITLOCK ENCODE AND AUDIO RECORD-REPRODUCE EQUIPMENT 4 Sheets-Sheet 4 Filed Jan. 21, 1965 24 Q START INVENTOR. BRUCE N. WH/TL OCK FIG. 8

AGENT United States Patent 3,354,557 ENCGDE AND AUDIO RECORD-REPRODUCE EQUIPMENT Bruce N. Whitlock, Morris, Plains, N.J., assignor to Me- Graw-Edison Company, Elgin, 111., a corporation of Delaware Filed Jan. 21, 1965, Ser. No. 426,989 9 Claims. (Cl. 35-6) ABSTRACT OF THE DISCLOSURE The invention relates to encode and audio recordreproduce equipment for teaching machines. Features of the invention reside in driving the record-reproduce head relative to a stationary record medium by means of a feed screw and a feed nut fixedly mounted on the head carriage in continuous engagement with the feed screw. The feed screw is coupled to a continuously running drive motor through a normally engaged drive clutch and an electrically controlled brake clutch of which the latter includes an intermediate shaft in the drive transmission which is uncoupled from the drive motor and braked against rotation when the brake clutch is deenergized and which is alternatively coupled to the drive motor and freed for rotation when the brake clutch is energized. A torsion spring connected to the feed screw serves to return the head carriage to home position when the drive clutch is disengaged. A commutator is driven during the recording and reproducing of each code signal. Each code signal comprises a start bit followed by a predetermined combination of recorded and nonrecorded bits and by read-out and stop intervals. The commutator is coupled to the intermediate shaft of the brake clutch by a onerevolution commutator clutch. The start-stop operation to record or reproduce each code signal is controlled by the brake clutch. The commutator clutch is engaged by pickup of each start bit so as to synchronize the commutator accurately with the drive of the head past the recorded and non-recorded bits of each code signal. The commutator clutch is set to be disengaged at the end of one revolution by the movement of the commutator through the read-out interval. The brake clutch is controlled by the commutator to stop the drive of the head carriage as the commutator enters the stop interval.

The invention relates especially to drive systems for teaching machines of the character disclosed in the pending Kobler et a1. application, Ser. No. 185,616, filed Apr. 6, 1962 (now Patent No. 3,281,959, dated Nov. 1, 1966), and entitled, Educational System and Apparatus. In such teaching machines the pointer of a card exhibiting equipment is advanced by steps along a printed medium to point out successive characters such as appear on the keyboard of a typewriter, and during each such advance a record-reproduce head of an encode equipment is advanced one interval to encode (free) the respective key of a typewriter and to activate a character pronouncing equipment. After the letters of a word or a sentence are so exhibited an audio equipment may be activated to make a statement, give instructions, etc., relative to the subject matter just shown to the pupil.

Each encode operation involves a quick start-stop operation of the drive system to advance the encode head approximately A word audio statement involves advancing an audio head along a recorded track. After each advance of the encode or audio head along the length of a respective track, the head is returned home and a rotation movement is produced between the head and record medium to bring the head into registration with a new track.

Objects of the invention are to provide encode and audio record-reproduce equipment for teaching machines which are simplified in construction and highly dependable in operation.

Other objects are to provide improved head driving systems suitable for both encode and audio recordreproduce equipment which have low start-stop inertia, freedom from repetitive speed fluctuations, and a fast feedback to home position after scanning to the end of each track.

The invention is herein particularly described in connection with an encode system for the abovementioned teaching machine with the intention that such description is illustrative as well of the use of the invention in a word audio record-reproduce equipment.

In the description of the invention, reference is had to the accompanying drawings, of which:

FIGURE 1 is a partial plan view of an encode apparatus for a teaching machine, showing portions broken away and other portions in sections;

FIGURE 2 is a rear elevational View of the encode apparatus shown in FIGURE 1;

FIGURE 3 is a fractional transverse section taken on the line 33 of FIGURE 1;

FIGURE 4 is a horizontal sectional view of the drive mechanism of FIGURE 1, taken on a medial horizontal plane through the shafts of the mechanism;

FIGURE 5 is a diagram showing a layout on a rectilinear basis of the commutator board of the encode system;

FIGURE 6 is an end view of the commutator board as seen from the left end of FIGURE 4;

FIGURE 7 is a fractional section taken on the line 7-7 of FIGURE 2; and

FIGURE 8 is a schematic circuit diagram of the encode system.

The encode mechanism shown in the accompanying drawings comprises a frame 10 including two parallel vertically arranged side plates 11 and 12 joined at the rear by a crossbar 13 and at the front by a crossrod 14. Extending leftwardly from the left side plate 11 are two spaced parallel frame plates 15 and 16 which are joined at their outer ends by 'a vertical frame plate 17. The plates 15 to 17 form a frame structure for the drive and control mechanism herein later described.

Slidably mounted on the crossrod 14 is a sleeve bearing 18 forming a portion of a head carriage. Press-fitted into a centralized position on this bearing is a wing collar 19 having upwardly and downwardly extending lugs 19a and 19b. Secured by screws 20 to the front side of the depending lug 19b is a block 21, and secured to the forward portion of this block is an inverted U- shaped bracket 22. The legs of this bracket are apertured to receive pivotally the side trunnions 23 of an encode head 24. This is a magnetic head having pole pieces 24a for contacting a magnetic record sheet 25.

Embracing the collar 19 is a yoke 26 whose side arms are slotted to receive the bearing 18. These arms are joined by a crosspiece 26a having an arm 26b extending rearwardly from the upper central portion thereof. Secured by screws 27 to the underside of the arm 26b is a block-shaped feed nut 28 having a threaded hole 28a receiving a feed screw 29. The feed screw spans the distance between the frame plates 11 and 12 and has reduced diameter end portions 29a forming shoulders which abut against the frame plates to hold the feed screw against end play. The end portions 29a extend through respective bearings in the end plates. Since the feed nut 28 is coupled in directions transversely of the machine to the head carriage the latter is propelled with a traveling movement in forward and reverse directions as the feed screw is turned in one direction and the other. Secured by screws to the rear face of the feed nut is a bracket 31 having a rearwardly extending arm at the trailing end of the head carriage to which is secured a stop member 32 adapted to abut against the frame plate 12 to define the home position of the carriage. Clarnped between the stop member and arm of bracket 31 is a clump of cantilever springs 33 of a fan shape (FIGURE 3) which extend beyond the stop member 32 to contact the side frame member 12 and cushion the return movement of the head carriage before the stop member strikes the side frame plate.

Secured to the upper lug 19a of the wing collar 19 is a rod 34 which extends rearwardly beyond the feed screw and on which is journaled a roller 35. This roller is interposed between two cross rods 36 and 37 staked at their ends in rocker arms 38 to form a head lift and pressure bail 3 9. Staked to the left rocker arm is a stud 40 journaled in the frame plate 11 and staked to the right rocker arm is a hollow stud 41 which receives and is connected by a' set screw 42 to a shaft of a rotary solenoid 43 mounted on the frame plate 12. A spring 44 is connected to another stud 45 on the right rocker arm so as to bias the bail 39 clockwise as it appears in FIGURE 3. By this bias action the head carriage is urged counterclockwise about the shaft 14 to press the magnetic head with a suitable contacting force against the record sheet 25. As the head carriage is returned home the solenoid 43 is activated to shift the head carriage clockwise so as to disengage the head 24 from'the record sheet.

The record sheet 25 is mounted on the back side of an exhibitor card 46 which in turn is secured to a transparent backing plate 47 carried at its ends by supporting blocks. 48 and 49. The block 48 has a threaded vertically-extending hole 48a receiving a feed screw and the block- 49 has a slot 49a receiving a guide rod 51. By turning the feed screw 50 the record card can be raised and lowered to cause the head 24 to register with selected transverse tracks on the'back face of the record sheet 25. The means'for so shifting the record sheet need not be herein described for puposes of the present inventiori.

The feed screw 29 is driven in a forward direction by a motor 52- to advance thehead carriage leftwardly as it appears in FIGURE 1. The motor 52 is end mounted on the horizontal frame plate 16 as shown in FIGURE 2. Secured to the shaft of the motor 52 is a worm 53" which meshes with a worm-wheel 53a (FIGURES 1 and 4) journaled on a shaft 54. This shaft is part of a brake clutch 55 hereinafter more fully described. The brake clutch has a housing 56 which is end mounted on a standard 57 upstanding from the frame plate 15. Pinned to the shaft 54 of the brake clutch 55 is a pinion gear 58 which meshes with a spur gear 58a pinned to a shaft 59. The shaft 59 is journaled at an intermediate point in the standard 57 and at its left end (FIGURE 4) in a bearing 60 carried by the end plate 17. The shaft 59 is supported in axial alignment with the feed screw 29 with freedom for axial shifting movement. Between the shaft 59 and feed screw is a single-tooth clutch 61 comprising a collar having a single-tooth 61a and an adjacent collar having a single tooth 61b, the two collars being pinned respectively to the feed screw and to the shaft 59. The shaft 59 is biased away from the feed screw to hold the clutch 61 normally disengaged by a spring washer 62 interposed between the standard 57 and a collar 63 pinned to the shaft 59. The shaft 59 is shifted to engage the clutch 61 by means of a rotary solenoid 64 (FIGURE 7) which is end mounted on the frame plate 16. A shaft 64a of the solenoid extends downwardly through an opening in the plate 16 and has secured thereto a yoke 65 provided with diametrically opposite pins 66 which engage a peripherally grooved collar 67 pinned to the shaft 59 to hold the clutch 61 engaged so long as the solenoid 64 is energized.

The worm wheel 53a is secured by screws 68 to an input gear flange 69 of the brake clutch 55. This brake clutch is, for example, a model MC unit of Autotronics, Inc., of Florissant, M0. The shaft 54 ofthis brake. clutch extends axially through the housing 56 beyond both ends thereof. Within'the housing is an input coil and clutch (not shown) which has such operation that when the coil is de-energized the gear flange 69 is free to turn on the shaft 54 and the shaft 54'is braked to the housing to lock the pinion gear 58 against turning, and when the coil is energized the input gear flange is clutched to the shaft 54 and the shaft is free to turn so as to couple the drive motor 52 to the pinion gear.

Whenever the machine is on standby for ready use, the motor 52 is left running, the clutch 61 is held engaged and the brake clutch 55 is rte-energized to lock the shaft 54LEa'ch instant the'brake clutch 55 is energized the rotating worn'l wheel 53a isjclutched to the pinion gear 58 to start driving the head carriage. As the head carriage is advanced the rotating feed screw winds up a spiral clock spring 711 secured at its inner end to a collar 72 fastened on the feed screw and secured at its outer end to a circular housing 73' mounted on the end plate 12. The instant the brake clutch 55 is deenergized the drive motor is uncoupled from the shaft 54 and the shaftis locked to the housing to hold the head carriage in its advanced positionagainst the returning force of the spring 71 on the feed screw. Thus, by intermittent energizations of the brake clutch55'the' head carriage is stepped across the record sheet2 5by successiveintervals. When the head carriage reaches the end'of its forward travel it open ates a switch 74 (FIGURES Z and 8)' carried by a bracket 75 on the end plate 11. The operation of this switch deactivates' the clutch solenoid 64 to disengage the clutch 6'1 and allow the feed s'cre'w 29" to be'turned in a reverse direction'by the clock spring 71 to return the headcar'riage quickly to home position. By means of a home switch 74b connected through a hold switch 6411 of the clutch'solenoid 64, as shown in FIGURE 8,

the clutch solenoid is kept de energized until thehead,

carriage reaches its home position.

Features of the invention reside particularly in providing a very coarse'feed scr'ew29 having a pitch of theorder' of the diameter of: the feed screw-typically .5" so that the'start-stop portion of the drive system comprising th'e shaft's'54 and 59, thege'ars' 58-5811 and the clutch 61 may have a relatively slow operating speed. Such slow operating speed reduces the start-stop inertia very greatly-since the inertia is proportioned to the speed squared''to allow the-head carr'ia'g'e' to come up to speed very quickly the instant the brake clutch is energized. This lower inertia also places less wear aiid andstrain on the brake clutch and other driveparts. A'

' further advantage of a drive feed screw with such very c'oarse thread is that it reduces the number of turns of the feed screw to advance the head carriage'through its' full range of travel, thereby allowing the use of a return clock spring. 71 of a convenient size commensurate with the other parts of the drive system.

Another feature of the invention is in using a feed nut 28 in constant engagement with the feed screw and in driving the feed screw through a single-tooth clutch 611 This assures that repetitive speed variations in the drive system such as fromthe'w'orm' 53-53i1, gears 58- 5821 and the feed' screw itself are synchronized in the positioning of the head along the track the same during reproducing as during recording" with the result that these variationsare ruled out as a means of producing errors in the record-reproduce process; Thus, these drive parts" need no't'be so precise or refined to provide a high quality of recording and reproducing of the'code signals as well-as of the word audio pronunciations, statements, instructions, etc;

During the entire advance of the head carriage along a track whether it is a continuous advance in audio recording or a step advance during encode recording, the clutch 61 is held in constant engagement to keep the shaft 54 of the brake clutch S5 in a fixed coupled relation to the feed screw. The coupling ratio is such that the shaft 54 is rotated slightly more than one revolution to advance the head carriage through a sufiicient interval-approximately %;"to record a code signal. This movement of shaft 54 is utilized to drive an encode commutator 76 through exactly one revolution during each encoding as will appear.

The encode commutator 76 comprises an armature 77 and a printed circuit board 78 as shown in FIGURE 6. The printed circuit board is supported by four posts 79 secured to the end plate 17. The armature is secured to a shaft 80 which has an outer bearing 81 in the commutator board and an inner bearing in a sleeve 82 pinned to the left end portion of the shaft 54 of the brake clutch 55 as shown in FIGURE 4. A clutch is provided between the shaft 80 and sleeve 82 in the form of a helical clutch spring 83 which frictionally embraces the outer end portion of the sleeve 82 and which is secured at its outer end to a collar 84 pinned to the shaft 80. The inner end of this clutch spring has a radially extending tang 83a which is normally held blocked by the end portion 85a of an armature 85 of a clutch electromagnet 86 mounted on the outer face of the end plate 17. This electromagnet has an L-shaped magnetic member 87 one leg of which is clamped to the base end of the central core and the other leg of which extends alongside the coil. The armature 85 is pivoted to this side leg of the magnetic member 87 and is extended past the front end of the core piece at a spacing therefrom under influence of a tension spring 88 which biases the armature outwardly against an overhanging lug $70 on the member 87. When the clutch electromagnet 86 is energized the armature 85 is drawn against the central core to move the outer end portion 85a of the armature out of blocking relation with the clutch spring tang 83a. This allows the clutch spring to turn, causing it to grip the sleeve and to turn the armature 77. If during a revolution of movement of the armature 77 the electromagnet 86 is de-energized to return the armature portion 85:: into a blocking position to the clutch tang 83a, the armature 77 will be stopped after one full revolution of movement.

The armature 77 com rises a radial arm 77a provided near its outer end with a transverse rod 89 of non-conducting material such as nylon into which are molded five spring brushes 90, 91, 92, 93 and 94. The tips of these brushes slidably engage the printed circuit board on a radius line at points circumferentially in line with respective pads of the printed circuit board. Thus, the brush 90 is in line with a set of pads P used in playback and with an erase pad E, the brush 91 with a set of pads R used in recording and with the erase pad E, the brush 92 with a send pad S and a home pad H, the brush 93 with a ground pad C and the brush 94 with a ground pad C The pads are connected to respective terminals along the edge of the printed board as shown in FIGURE 8. The brushes 90, 91 and 94 are interconnected by a jumper 95, and the brushes 92 and 93 are interconnected by a jumper 96. As will appear, during recordingthe pads P are out of circuit and during reproducing the pads R are out of circuit. The pads are distributed around the board in the manner indicated by the rectilinear layout in FIGURE 5. In the starting position of the armature shown in FIGURE 8, the erase pad E is connected to ground C and the home pad H is connected to the ground pad C The armature 77 moves counterclockwise and when it passes its zero position the start pad ST is connected to ground C and the connections are broken to the send and home pads. In the next successive intervals the pads R to R are connected successively to ground pad C and next the erase pad E is connected to ground pad C During traversal of the central portions of the start pad ST and of the pads R to R the pads P to P are traversed and connected also in succession to the ground pad C but as aforestated the pads P are out of circuit during recording and the pads R are out of circuit during reproducing. After traversal of the pad P and during traversal of the first portion of the erase pad E the send pad S is connected to ground pad C and during traversal of the remaining portion of the erase pad E the home pad H is connected to the ground pad C The operation of the present system during recording is herein next described with reference to the schematic diagram of FIGURE 8. At the outset, the armature 77 is at rest in a start position, as shown, wherein it completes the circuit of a home relay 97 via the home pad H, ground pad C and ground 98 to activate this relay and hold open its a and b contacts. To condition the machine for recording, a record-reproduce relay 99 is first activated from a positive terminal 100 to ground 181 by closing switch 990. Activation of this relay throws a bank 102 of twelve RR switches marked RR to RR to their rightward or record contacts. A first result of this switch operation is to open switch RR in a circuit 163 to disable a translator mechanism 1% partially diagrammatically represented. As described in the aforestated pending application 185,616 this translator mechanism includes a series of six solenoids and respective permutation bars controlled by switches 1 to 6 of the translator mechanism to release respective keys of a typewriter from a blocked condition as the switches are coded-i.e., operated in selected combinations. When the entire translator mechanism 104 is disabled by opening the common ground line 103 all of the keys are unlatched to allow any key to be depressed at will. Such typewriter may be a Flexowriter manufactured by Friden, Incorporated, of San Leandro, Calif. The typewriter has not only the selective key blocking means just described but also a bank 105 of transmitting switches including a start switch 105s and a series of six code switches SW to SW such that when a key is depressed the start switch 105s and one or more of the code switches SW are closed according to a binary code. These transmitting switches are used during recording to record code signals on the record sheet 25 which code signals are later reproduced to selectively unblock respective keys of the typewriter.

In the start position of the armature 77 of the commutator 76, which the armature occupies before a key of the typewriter is depressed, the armature also connects an erase oscillator 106 to the record head 24 via a circuit from ground 107, through erase oscillator 106, lead 10 8, erase pad E, brush 91, jumper 95, brush 94, ground pad C lead 109, switch RR right contact, jumper 110, switch number RR right contact, lead 111, head 24 and ground 112. Also, when all of the keys of the typewriter were unlatched, a switch 113 in series with a start relay 114 of the encoder is held open by means not herein necessary to show. (As will later appear, the switch 113 is operated during reproducing by each release of a key of the typewriter.) When the switch 113 is held open the start relay 114 is under control of an alternative activating circuit 115, This alternative activating circuit is prepared for operation by the closing of switch RR as the machine was conditioned for recording. This alternative activating circuit runs from plus terminal 116 via the relay 114, switch RR and start switch 1415s to ground 117. Thus, the start relay 114 will be operated the instant the operator presses a key of the typewriter. Operation of the start relay closes a hold switch 114a without any immediate effect because this hold switch is in series with a switch 97b now held open by operation of the home relay 97 as before described, and it closes a start switch 7 114b to activate the brake clutch 55 from plus terminal 118 to ground 119. Activation of the brake clutch frees the shaft 54 and clutches the same to the motor 52 to start driving the head carriage.

The operation of the code Switches SW to SW in a selected combination as a key of the typewriter is depressed causes operation of a corresponding combination of bit relays B. For instance, if it is assumed that code switches SW and SW are operated as a particular key is depressed then the bit relays B and B are activated from ground 117 to plus terminal 120. Operation of these bit relays closes respective hold switches EH and EH but without immediate hold effect because these hold switches are in a common hold circuit 121 leading to ground 122 .via the switch 97a now held open because at the outset the home relay 97 is activated as before described.

The operation of the bit relays B and B also throws respective record switches BR and BR from their upper to lower contacts to disconnect the erase oscillator 106 and to connect a record oscillator 123 from ground 107 to the respective pads R and R of the commutator 76. Also, the bit relays operate respective switches BM and BM in the translator 104 but during record the operation of these switches is without any effect because the common ground lead 103 of the translator mechanism is held open by switch RR of the bank 102 as before described.

As the head 24 starts moving it begins erasing the record medium by current from the erase oscillator 106. This erasure continues until the armature 77 is moved off the erase pad E-which is for a duration of only about 27 milliseconds maximum since the armature 77 is started rotating simultaneously as the drive of the head 24 is startednThe clutch 83 for starting rotation of the armature 77 is engaged by activation of the clutch solenoid 86 from plus terminal. 124 via switch 125a of the send relay 125 now not operated, lead line 126, switch RR jumper 127, switch RR start switch 105s and ground 117. As the clutch solenoid 86 is operated it draws the clutch arm 85 free of the spring tang 83a to engage the clutch spring 83 and it closes the hold switch 86a to provide an alternative ground 128 for the solenoid via the switch 125a of the send relay.

The instant the commutator armature 77 passes the zero point where it leaves the erase pad E, erase current to the head 24 is cut off and the circuit of the home relay 97 is opened to drop this relay. The dropping of the home relay closes its switch "a to complete the hold circuit for the bit relays B then standing activated, and it closes its b switch to complete the hold circuit for the start relay 114. This means that the drive for the head 24 and of the commutator 76 are locked in, as are the operated bit relays B, until the armature 77 completes one revolution of movement.

During the ensuing one revolution of rotation of the commutator armature 77 the P pads are all out of circuit by reason of the switch bank 102 being in its record position. The start pad ST is connected to the record oscillator 123. Further, the R pads corresponding to the activated bit relays B are connected to the record oscillator 123 and the R pads corresponding to the bit relays not now activated are connected to the erase oscillator 106. This means that following the brief erase interval there is placed on the record sheet a start bit as the armature 77 traverses the start pad followed then by one or more record bits at space intervals corresponding to the activated bit relays and by erasures at the space intervals corresponding to the non-activated bit relays. For the illustrative example above-considered there would be record bits in the first and third intervals and erasures in the second, fourth, fifth and sixth intervals.

When the armature 77 reaches the send pad S- which is just before it has moved off the R pad it connects the send relay 125' to ground 98 to activate this relay.

The resultant opening of the switch 125a drops the clutch solenoid 86 to return the clutch armature in position to open the clutch 83 when the clutch has completed one revolution of movement of the armature 77 and it closes a switch 1251: now however without elfect because this switch is in a ground circuit 103 of the translator mechanism already open. The armature 77 therefore continues in its counterclockwise rotation until it reaches its start position shown in FIGURE 8. As the armature moves onto the erase pad E it again begins feeding erase current to the head 24 and as it enters onto the home pad H it activates the home relay 97. This opens the switch 97a to drop the bit relays B then standing operated and it opens a switch 97b to drop the start relay 114. As the start relay 114 is dropped it opens a switch 114a without efiect because the hold circuit is already open and it opens a switch 114b to deactivate the brake clutch 55. This deactivation of the brake clutch 55 uncouples the motor from the shaft 54 and clutches this shaft to the frame of the machine to stop the forward drive of the head 24 and to hold the head in its advanced position against the force of the return spring 71. In all, the head is advanced approximately during the one revolution of the commutator armature 77 responsive to depressing a key of the typewriter. In that interval the head has recorded a start bit followed by one to six record bits in respective space intervals depending on the binary code of the key which was depressed.

The above sequence of operations will reoccur following each depressing of a key of the typewriter, with the head advancing one interval responsive to each key depression. When the head has reached the end of its travel it opens the switch 74 to disengage the drive clutch 61 and allow the clock spring 77 to return the head to home position. Alternatively, the switch 74 can be openedby auxiliary means (not shown) to return the carriage from any position in its travel.

When the encoder is used as a reproducer the successive code signals are reproduced to unlatch the respective keys of, the typewriter. Upon depressing an encoded key the next combination of recorded bits is reproduced to unlatch a next key, etc. To shift the machine to reproducing condition the RR switch 99a is opened thereby returning the switch bank 102 to the position shown in FIGURE 8. As the switch bank 102 is so returned to reproduce position the following results occur :(1) switch RR; connects the head 24 now operating as a reproducer through amplifier 129 and relay 130 to ground 131, (2) switch RR connects the ground pad C of the commutator 76 to the ground side 126 of the clutch solenoid 86 now in open circuit, (3) switch RR disables the start circuit 115, (4) switches RR through RR connect the bit relays B through B respectively to the P pads P through P and (5) switch RR prepares the common ground circuit 103 for the translator 104. Further, the home relay 97 again stands operated at the outset as shown. To start the machine to read a code signal for the first character to be typed, the attendant momentarily closes the switch 113. This activates the start relay 114 which in turn activates the brake clutch 55 to start driving the head 24. Immediately, the head picks up the start bit to activate the relay 130 which closes switch 130a to connect ground 132 via lead line 126 and switch a to clutch solenoid 86 whereby to engage the clutch 83 and start rotation of the commutator armature 77. Since the commutator armature 77 is started by the start bit of each code signal, the drive of the commutator is synchronized anew with the drive of the reproducer head at the start of picking up. each code signal. This synchronizing of the commutator with the drive of the head as to each code signal eliminates accumulative variations along the length of a code track-which may contain as many as 50 code signalsas a source of error; further, it reduces greatly the tolerance requirements on the drive mechanism and on the stability of the magnetic record sheet. For example,

when a six bit code signal is recorded within a length of .187", a :few thousandths variation from a correct positioning of the head during the reproducing of a code signal may cause serious error. Variations Within this limitation can arise due to dimensional changes from thermal and humidity effects especially on the magnetic record sheet or from variations in the lead screw end play, etc. Further, variations beyond these tolerance limitations are very likely to occur when magnetic record sheets are interchanged between different machines. The synchronizing of the commutator with the drive of the head as to each code signal presents therefore distinct advantages over the prior art arrangements wherein the feed screw is utilized as a measuring instrument along the length thereor relative to the magnetic record sheet.

Accordingly, when a recorded bit is picked up the armature 77 will be registering with the playback pad P corresponding to the space interval of the recorded bit. For the illustrative example of recorded bits in the first and third intervals, a signal will be fed from the head to close the switch 135a during the start bit and during the intervals when the armature 77 is registering with the P and P pads. Ground 132 is therefore carried through the commutator to activate the corresponding B and 13;; bit relays. As these relays are activated they find hold circuits via the hold line 121. Their activation of the BR switches 1 and 3 is now without effect, but their actuation of the BM switches 1 and 3 has now the effect of preparing the translator 104 by means not shown to unlatch the key of the typewriter whose code signal has been just read. The full code signal will in all cases have been read when the armature 77 reaches the pad P but it is not until the armature 77 reaches the send pad S that the send relay 125 is operated to close the switch 125]) in the translator circuit 163 and cause the translator solenoids to be operated to unlatch the key of the typewriter corresponding to the code signal just read. This operation of the send relay also drops the commutator clutch solenoid 86 to stop the armature 77 when it has completed one full revolution of movement. In the final movement of the armature 77 it moves off the send pad S to drop the send relay and onto the home pad H to operate the home relay 97 both to drop the start relay 114 and the bit relays then standing activated. This returns the machine to its original start condition to make it ready for reading another code signal. It is by the release of the key of the typewriter last encoded that the start switch 113 is again operated momentarily to activate the start relay 114 and start again the whole operation of reading the next code signal to encode (free) another key of the typewriter. Thus, a new key is encoded immediately upon the release of the key last encoded. This continues with the head being stepped along as successive encoded keys are depressed until the head reaches the end of its travel whereupon it again drops the clutch solenoid 64 to disengage the clutch 61 I and allow the head to be returned to home position by the return spring 71.

The embodiment of my invention herein particularly shown and described is intended to be illustrative and not necessarily limitative of my invention since the same is subject to changes and modifications without departure from the scope of my invention, which I endeavor to express according to the following claims.

I claim:

1. A drive mechanism for the record-reproduce headcarriage of a teaching machine comprising means mounting said head carriage for movement along a track on a record medium, a feed screw extending along the path of said head carriage, a feed nut fixedly mounted on said head carriage in continuous engagement with said feed screw, a drive system including a drive motor for rotating said feed screw to advance said head carriage, a torsion spring connected to said feed screw and wound up by the feed screw during the advance movement of the head carriage, an electrically energizable brake clutch in said drive system for holding the feed screw against a reverse rotation by said spring when the brake clutch is deener. gized, a normally engaged drive clutch in said drive system between said feed screw and brake clutch, means for selectively energizing said brake clutch to cause said carriage to be advanced by said drive motor by predetermined step distances, and means operated by said carriage when the same is advanced to a predetermined end point in its travel for disengaging said drive clutch to free the feed screw and allow the same to be driven in a reverse direction by said spring whereby to return the head carriage to home position.

2. In a teaching machine: the combination of a record medium having a track prerecorded with successive items of information, a reproduce head for scanning said track, a carriage for said reproduce head mounted for movement along said track, and a drive system for intermittently advancing said head carriage by successive steps each sufiicient to cause said head to scan a respective prerecorded item of information at a predetermined steady speed and to return the head carriage quickly to home position when it reaches an end point in its forward travel, comprising a feed screw extending along the path of said head carriage, a feed nut fixedly mounted on said carriage in continuous engagement with said feed screw, a drive motor, a torsion spring having a fixed connection to said feed screw for turning said feed screw in a reverse direction, a coupling between said drive motor and feed screw for turning the feed screw in a forward direction, said coupling including a normally engaged drive clutch and a brake clutch between said drive clutch and drive motor, said brake clutch including means to hold the feed screw from being turned in a reverse direction by said spring when the brake clutch is disengaged to uncouple the drive motor from said feed screw, said spring being operative to rotate said feed screw to return said carriage to home position when said drive clutch is disengaged, and said feed screw having a coarse pitch to bring said carriage quickly to normal speed when the brake clutch is engaged and to reduce the drive range of said spring in returning said head carriage to home position.

3. A drive system for the record-reproduce head of a teaching machine comprising a carriage for said head mounted for back and forth traveling movement, a continuously rotating drive motor, a feed screw extending along the path of said head carriage, a feed nut fixedly mounted on said carriage in continuous engagement with said feed screw, a step-down transmission between said motor and said feed screw including an intermediate shaft, a brake clutch between said motor and intermediate shaft for alternatively connecting the motor to the shaft and for disconnecting the motor from the shaft and concurrently braking the shaft against rotation, a drive clutch between said intermediate shaft and said feed screw, means for normally holding said drive clutch engaged, torsion spring means connected permanently to said feed screw for constantly urging the same in a reverse direction to return said head carriage to home position when said drive clutch is disengaged, a first circuit means for selectively energizing said brake clutch, and other circuit means controlled by said carriage for disengaging said drive clutch when the carriage reaches a predetermined point in its advance movement whereby thereupon to cause the carriage to be returned to home position by said spring means.

4. The drive mechanism set forth in claim 3 wherein said first circuit means is effective when energized to start a forward drive of said head carriage and when deenergized to stop said forward drive and lock said shaft to hold said head carriage in its advanced position against return movement by said spring means, including a start relay activatable to supply energizing current to said brake clutch, a hold circuit closed by activation of said start relay to hold the start relay activated, a commutator, a clutch for coupling said commutator to said shaft, means responsive to activation of said start relay for engaging said commutator clutch, and means responsive to one revolution of said commutator for opening said hold circuit to drop said start relay and disengage said commutator clutch.

The drive mechanism set forth in claim 4 wherein said commutator clutch is of a one-revolution spring type, including a clutch solenoid having an armature in position when the solenoid is deactivated to hold said commutator clutch disengaged, means for concurrently activating said start relay and said clutch solenoid, means responsive to a fractional revolution of movement of said commutator for dropping said clutch solenoid to stop said commutator after one revolution of movement, and means responsive to substantially one revolution of movement of said commutator for dropping said start relay to deenergize said brake clutch.

6. In a teaching machine including a record medium having an encode track with prerecorded code signals for respective characters, each of said code signals comprising a start bit followed by a predetermined combination of recorded and non-recorded bits and by read-out and stop intervals in the sequence named: the combination of an encode head, drive means including a startstop clutch for advancing said head along said track, a bit relay for each of said combination of recorded and non-recorded bits, a commutator having a rotary armature and cooperating successive terminals connected to said bit relays respectively, a drive transmission operable by said drive means for moving said commutator armature past said terminals in synchronism with the movement of said head past said successive recorded and nonrecorded bits, said drive transmission including a commutator clutch, means for engaging said start-stop clutch to start the drive of said encode head, means operable by the start bit picked up by said encode head to engage said commutator clutch to start rotation of said armature whereby to cause those bit relays to be operated which correspond to the recorded bits of the code signal, means controlled by said commutator as the armature is moved into said read-out interval for completing a send circuit for said operated bit relays and for setting said commutator clutch to become disengaged when the armature reaches said stop interval, and means controlled by said commutator as the armature is moved into said stop interval for disengaging said start-stop clutch to stop the drive of said encode head.

7. In a teaching machine including a record medium having an encode track bearing a series of prerecorded code signals for respective characters, each of said code signals comprising a start bit followed by a predetermined combination of recorded and non-recorded hits: the combination of an encode head, drive means including a start-stop clutch for advancing said head along said track, a bit relay for each of said combination of recorded and non-recorded bits, a commutator having a rotary armature and cooperating successive terminals connected to said bit relays respectively, a drive transmission operable by said drive means for moving said commutator armature past said terminals as said head is moved past said successive recorded and non-recorded bits, said drive transmission including a commutator clutch, means for engaging said start-stop clutch to start the drive of said encode head, and means operable by the start bit of each code signal picked by said encode head to engage said commutator clutch whereby to synchronize anew the movement of said armature past said terminals with the movement of said head past the successive recorded and non-recorded bits of each code signal 8'. The teaching machine set forth in claim 7 wherein each of said code signals also includes read-out and stop intervals following the last of said bits, said drive of said commutator being adapted to require the head to move through said read-out interval and into said stop interval to complete one revolution of said commutator, said commutator clutch being of a one revolution type, includ ing circuit means controlled by said commutator as it moves through said read-out interval to set said commutator clutch to disengage at the end of said one revolution oi said commutator.

9. The teaching machine set forth in claim 8, including means controlled by said commutator as it is moved into a stop interval to disengage said start-stop clutch and to hold said head in its advanced position.

References Cited UNITED STATES PATENTS 3,128,563 4/1964 Kobler 3'56 3,145,268 8/1964 Whitney et al -5 3,281,959 11/1966 Kobler et al. 35-6 EUGENE R. CAPOZIO, Primary Examiner.

W. W. NIELSEN, Assistant Examiner. 

1. A DRIVE MECHANISM FOR THE RECORD-REPRODUCE HEADCARRIAGE OF A TEACHING MACHINE COMPRISING MEANS MOUNTING SAID HEAD CARRIAGE FOR MOVEMENT ALONG A TRACK ON A RECORD MEDIUM, A FEED SCREW EXTENDING ALONG THE PATH OF SAID HEAD CARRIAGE, A FEED NUT FIXEDLY MOUNTED ON SAID HEAD CARRIAGE IN CONTINUOUS ENGAGEMENT WITH SAID FEED SCREW, A DRIVE SYSTEM INCLUDING A DRIVE MOTOR FOR ROTATING SAID FEED SCREW TO ADVANCE SAID HEAT CARRIAGE, A TORSION SPRING CONNECTED TO SAID FEED SCREW AND WOUND UP BY THE FEED SCREW DURING THE ADVANCE MOVEMENT OF THE HEAD CARRIAGE, AN ELECTRICALLY ENERGIZABLE BRAKE CLUTCH IN SAID DRIVE SYSTEM FOR HOLDING THE FEED SCREW AGAINST A REVERSE ROTATION BY SAID SPRING WHEN THE BRAKE CLUTCH IS DEENERGIZED, A NORMALLY ENGAGED DRIVE CLUTCH IN SAID DRIVE SYSTEM BETWEEN SAID FEED SCREW AND BRAKE CLUTCH, MEANS FOR SELECTIVELY ENERGIZING SAID BRAKE CLUTCH TO CAUSE SAID CARRIAGE TO BE ADVANCED BY SAID DRIVE MOTOR BY PREDETERMINED STEP DISTANCES, AND MEANS OPERATED BY SAID CARRIAGE WHEN THE SAME IS ADVANCED TO A PREDETERMINED END POINT IN ITS TRAVEL FOR DISENGAGING SAID DRIVE CLUTCH TO FREE THE FEED SCREW AND ALLOW THE SAME TO BE DRIVEN IN A REVERSE DIRECTION BY SAID SPRING WHEREBY TO RETURN THE HEAD CARRIAGE TO HOME POSITION. 